<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<script>
		/* 	var x=10;
			console.log(x);
			{
				var x=100;
				console.log(x) 10;
			}
			console.log(x); 100 */
			//es6的新标准
			let x=10;
			console.log(x);
			{
				
				let x=100;
				console.log(x);
			}
			//代码段中let定义变量作用域 代码段结束
			//里面的x也结束
			console.log(x);
			//js只有变量没有常量定义，es6定义常量
			const sysname="学生管理系统";
			console.log(sysname);
			
			const PI=3.14;
			console.log(PI);
			PI=3.1415926;
			
		</script>
	</head>
	<body>
	</body>
</html>
